Priority is claimed on Japanese Patent Application No. 2005-95479, filed Mar. 29, 2005, and Japanese Patent Application No. 2005-219027, filed Jul. 28, 2005, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a radar system and a computer program to be used therefor. In particular, it relates to a vehicular electronic scanning millimeter wave radar system and a computer program ideally suited for detecting objects.
2. Description of the Related Art
Heretofore, for a vehicular electronic scanning millimeter wave radar system, there are known beam scanning methods, of a mechanical type that scans a single beam mechanically in the horizontal direction, and of an electric type (for example refer to Japanese Unexamined Patent, First Publication No. H06-88869) that scans a plurality of beams electrically in the horizontal direction. However, in either one of the methods, in the case where there are adjacent objects, it is necessary to narrow the width of the beam to be transmitted from a transmission antenna in order to improve the separation function of the objects in the horizontal direction.
For example, FIGS. 7A and 7B shows the case where transmission waves are transmitted from a transmission antenna of an electronic millimeter wave radar system installed in a following vehicle, and incoming waves from two vehicles in front are received by a three channel receiving antenna. However, as shown in FIG. 7B, in the case where the width of the beam of a transmission wave is wide, the central beam of the received incoming waves (received waves) consists of incoming waves (received waves) received from both of the vehicles in front. Hence the difference in the levels between the channels is small. Consequently, the separation function deteriorates, and hence there is a problem in that the two vehicles in front cannot be captured accurately.
Therefore, in order to solve the above problem, as shown in FIG. 7A, it is necessary to narrow the width of the beam of the transmission wave in order to increase the difference in the levels of received waves from adjacent channels. However, in order to realize this, it is necessary to increase the areas of the transmission antenna and the reception antenna (for example, refer to pages 188 to 191 of “Antenna Technology Handbook” compiled by the Institute of Electronics and Communication Engineers of Japan, published Sep. 30, 1991).
As described above, in order to improve the separation function, it is effective to increase the areas of the transmission antenna and the reception antenna, and to narrow the width of the beam. However, if the areas of the transmission antenna and the reception antenna are increased, there is a conflicting problem in that it is difficult to miniaturize the whole system, and to reduce the cost.
The present invention takes the above problems into consideration with an object of providing a radar system and a computer program, that improve the separation function of objects in the horizontal direction regardless of the width of the beam transmitted from a transmission antenna.